Zone 2

By Peaks Coaching Group Elite/Master Coach, David Ertl

https://www.peakscoachinggroup.com/DavidErtl

I’m seeing a lot of interest in Zone 2* training lately, not only from cycling training circles but also from the longevity and aging sectors. Cyclists have long known the benefits of Zone 2 training for building aerobic capacity and endurance.

One of my favorite graphs from the book ‘Training and Racing with a Power Meter’ by Hunter Allen et al, is Table 3.2, shown here:

This chart shows the physiological adaptations from training in each of the 7 zones.  Zone 2, also called the Endurance zone, is useful for building aerobic capacity and endurance, things like increased capillarization, mitochondrial function, fat metabolism and conversion of Type IIx (fast glycolytic) to Type IIa (fast oxidative) muscle fibers. If you are training for a long-distance event, there is no substitute for doing long steady Zone 2 rides, sometimes also referred to as LSD (Long Steady Distance) or base miles.

To elicit these above-mentioned adaptations requires long hours in the saddle. The intensity is low, so the benefit comes not from the intensity but from the time spent at this intensity. The benefit from Zone 2 training is achieved by fatiguing the aerobic system, which takes time. How long depends on one’s fitness.  For a beginner, an hour may be considered long, but as fitness builds, the required length of these rides also increases.  For a very fit cyclist, it may take four or more hours to begin to elicit the stress necessary to improve on these adaptations. As the type I fibers become fatigued over time, the type II fibers are recruited to assist, even though the intensity hasn’t necessarily increased.

According to this chart, it requires at least 2.5 hours of Zone 2 training to begin to accumulate enough stress to generate the Zone 2 adaptations mentioned above (again, depending on your fitness level, someone that regularly rides 2.5 hours probably will need 4-5 hours of riding to improve their endurance).  This raises the question as to whether there is any value in doing shorter Zone 2 rides as you increase your fitness levels.

I’ve heard the argument that short Zone 2 rides can be used to add volume and stress to one’s training schedule. But if you want to build volume and have an hour, why not do something that will generate more stress and elicit some real benefit, such as Zone 3 or above work?  If you just want to loosen the legs, then why not do an hour of Zone 1 recovery work? Zone 2 rides probably won’t elicit much of the desired training effect if they are too short to generate fatigue. Then one needs to assess what the goal of that training session really is.

‘Junk miles’ is a common term to describe rides that add fatigue but don’t generate enough of a training effect to warrant this fatigue. Junk miles have traditionally been called ‘no-man’s land’ training, which is now considered to be Zone 3.  The argument was that this is not hard enough to generate significant stress but generates fatigue.  This argument is used today by those in opposition to sweet spot training. But refer again to the first chart above and see the many benefits that can accrue from Zone 3 training, again assuming the duration is long enough to elicit these benefits. These are at least as good as the benefits that come from Zone 2 training, and in some aspects better than Zone 2. 

As I’m creating training plans for my athletes, every workout I put in the plan has a purpose.  Whether it’s for endurance (Zone 2), FTP (Sweet Spot or Zone 4), anaerobic capacity (Zones 5 and 6), or simply recovery (Zone 1), there is a reason for including these workouts. My definition of ‘junk miles’ is a little different from that above: junk miles are any miles that are ridden without a purpose. So, this brings us back to the question of what to do when one only has a hour to train.  Well, according to the second chart above, that indicates that the work should be in Zone 4 or higher to elicit some benefit during this duration.  Or if you don’t want to work that hard, then I’d recommend just doing an hour or less of Zone 1 recovery work. Doing an hour of Zone 2 or low Zone 3 isn’t likely going to add any physiological benefit but will only add fatigue. Now, if the purpose is to add fatigue, then maybe that’s acceptable, but just realize you aren’t really going to achieve any substantial training benefit other than fatigue development. What if you say you just want to go out and burn some calories, isn’t an hour of Zone 2 good for that?  Well, yes, but you can burn even more calories riding in Zones 3 and above if that is your objective. What if your purpose is to go out and have a fun, relaxing ride? I do this on occasion, and it is good for the mind and the soul. If you happen to want to ‘just ride’ and enjoy yourself and want to ride a little harder than Zone 1, then you’ve achieved that purpose by doing a short Zone 2 ride. The point is to make sure you know what your training objective is for each ride and then do the ride that accomplishes that. But also realize the limitations of each type of ride in terms of the training benefit.

David has been a long time coach with Peaks Coaching Group and has an impressive list of results.

To contact David, please send an email to info@peakscoachinggroup.com with your questions.